A variety of headphone apparatuses of relatively high sound quality and of large size have been proposed; and typically, in order to generate an acoustic field space for naturally resonating in a back housing where a driver unit is housed, an headphone apparatus using a solid zelkova wood and the like are sold, however, the housing portion and ear pad portion thereof are large to cause an increase in weight.
FIG. 6 is a side sectional view showing a back housing portion used for a conventional headphone apparatus which is large and of high sound quality, shown in Patent Literature 1.
In FIG. 6, reference numeral 1 denotes an approximately circular or elliptical baffle board formed of material such as synthetic resin or wood through which no sound is transmitted.
A driver unit 5 is opposed to or fitted into a through-hole 4 made in the approximate center of this baffle board 1.
The driver unit 5 has a structure of an electrodynamic type in which a voice coil 5C fixed to a domed diaphragm 5A is driven between a magnet 5B and a concave yoke 5D, similarly to a typical loudspeaker.
A plurality of air ventilation holes 6A, 6B, . . . are made with the through-hole 4 made in the center of the baffle board 1; and a highly air-permeable ventilation member 9 made of sponge, unwoven fabric or the like is attached to each of the through-holes 6A and 6B.
A domed back housing 2 covers the back surface of the baffle board 1 and is integrated with the baffle board 1 to form a housing 3 as a baffle portion.
A ventilation hole 7 is made in the back surface (top) of the housing 2, and a ventilation member 9 is attached similarly to the ventilation holes 6 in the baffle board 1 to enhance the baffle effectiveness. Nonferrous metal, synthetic resin, solid zelkova that is a wooden material as described above or the like is selected for the back housing 2, and an acoustic field space is made large to improve sound quality.
On the front surface of the baffle board 1 is provided an ear pad 8 in which an approximately ring-shaped cushion member made of sponge or the like is surrounded by an outer skin 10 made of synthetic resin, leather, cloth, or the like.    [Patent Literature 1] Published Utility Model Application No. H5-36991 (FIG. 6)